WASHINGTON (Reuters) - A majority of Republican lawmakers in the tightest congressional races are changing their message on guns, expressing new support for restrictions after last month’s high school shooting in Florida, according to a Reuters review of the candidates’ public statements.

Eleven Republican incumbents face elections in 2018 widely seen as toss-ups or leaning against the current office holder. So far, six of them have publicly embraced new gun control measures in the wake of the Feb. 14 shooting in Parkland, Reuters found. (Graphic: http://tmsnrt.rs/2I8qevA)

In advocating for some restrictions, they are breaking ranks with a party that has often balked at taking significant steps that could restrict Americans' constitutional right to own guns and has typically limited its responses to mass shootings to expressions of sympathy.

However limited the shift, it shows that lawmakers who will depend on the votes of moderates and independents to win tough swing-district races are deviating from decades of party orthodoxy on gun ownership.

They are doing it amid a public outcry over repeated mass shootings that has been driven in part by student activists who have confronted lawmakers over legislative inaction on the issue.

In less competitive races, most Republican candidates are still holding to the party position on guns. Most Republican lawmakers were largely silent last week when President Donald Trump surprised his party with his call for new limits on gun ownership, including a directive to ban so-called bump stocks that make semi-automatic rifles fire more quickly.

Don Bacon, a first-term congressman for Omaha, Nebraska, is one of those lawmakers facing what is shaping up to be a hard-fought race in November's congressional elections. After a former student shot dead 17 people at the Florida high school, he expressed support for tighter restrictions on Americans’ ability to buy and own guns.

In social media posts and interviews, he departed from the message of the National Rifle Association, which is a major donor to the Republican Party and has given Bacon one of its highest ratings.

Bacon said he was working on legislation to raise penalties for illegal gun buyers. He also wanted to improve background checks and allow law enforcement officers to temporarily seize firearms from people believed to be dangerous, after those people are allowed to contest the claims against them.

After a gunman shot dead 58 people at an outdoor concert in Las Vegas in October, Bacon was more cautious: He joined 78 lawmakers from both parties in signing a letter urging the Bureau of Alcohol, Tobacco, Firearms, and Explosives to reevaluate bump stocks. The NRA also supported the move.

"It's not about winning re-election. It’s about doing what’s right,” the congressman told Reuters of his post-Parkland support for new measures. At the same time, he emphasized that he views himself as a defender of the gun rights enshrined in the Second Amendment of the U.S. Constitution.

AMERICANS FAVOR RESTRICTIONS

Three out of four Americans say they favor banning military-style assault weapons, a recent Reuters/Ipsos poll found. The poll of 1,488 people between Feb. 25 and March 1 also found that nearly 9 in 10 people supported expanding background checks for gun buyers.

Republican incumbents in competitive districts need to respond to voters who are often more open to gun restrictions than those in districts that are easy wins, said Ryan Williams, a Republican strategist at FP1 Strategies.

"In swing districts, voters have different opinions and they want to see a more comprehensive approach," Williams said.

Because concern in the United States over mass shootings is high, adopting more restrictive views on gun policy could help candidates in tight races, said Doug Heye, another Republican strategist. But Republican lawmakers also want to avoid alienating gun rights supporters, said Williams.

Underscoring that, in another 13 races, where Republican incumbents face competitive but not toss-up races, only three of the Republicans have moved toward gun control, according to the Reuters review.

NOTICEABLE SHIFTS

Dana Rohrabacher is another congressman and gun rights stalwart facing a tough fight to keep his seat. The Southern California Republican has also noticeably shifted his positions. He now says it should be illegal to sell weapons to felons and people taking psychiatric prescription drugs.

By contrast, after the Las Vegas shooting, Rohrabacher’s spokesman Ken Grubbs said it was “demagoguery” to discuss specific legislative changes, according to a report in a local Californian newspaper. Grubbs did not return a request for comment from Reuters.

Congressman John Faso of upstate New York said in interviews after the Florida shootings that he favors expanding background checks and not allowing people to buy semi-automatic guns until they turn 21.

Faso, who took office in 2017, confined his response to the Las Vegas shootings to a Twitter post in which he described them as “heart breaking.”

Bacon, Rohrabacher and Faso and eight other Republican incumbents face the toughest re-election fights, according to three political analysis groups - Cook Political Report, Larry Sabato's Crystal Ball and Inside Elections.

Republican lawmakers in seven "safe" districts adjoining those districts have largely stuck to the same positions they had before the shooting: mostly opposed to new forms of gun control.

Some defended their decision to not endorse new restrictions when contacted for comment by Reuters. Congressman Ken Buck of Colorado said he has seen no evidence to justify new laws restricting the purchase or ownership of guns. None of the other lawmakers contacted by Reuters besides Bacon and Buck offered an explanation for their shift or steadfastness on gun policy following Parkland.

Reuters examined the public statements of 31 lawmakers in the competitive and safe districts, including speeches and social media postings, and asked them about any other pronouncements they have made on the issue.

NRA DECISIONS TO COME

The stark difference in responses can be seen in Florida. Republican congressman Carlos Curbelo is in a tight race in his South Florida district. He said he now favors raising the age of purchase for long guns and even advocates banning civilian purchases of military-style weapons and regulating high-capacity magazines.

The 18 Republican lawmakers in both competitive and safe seats whose statements Reuters analyzed have received more than $1.5 million from the NRA in donations or expenditures on their behalf throughout their political careers. The 11 lawmakers who did not shift their stance on gun control after the Florida shootings received 85 percent of that, Reuters found.

Asked whether the NRA was considering limiting support for any of the lawmakers who have expressed support for new gun control measures, NRA spokeswoman Jennifer Baker said the association had yet to complete its evaluations of candidates. This would be done after election registration deadlines, which have not yet passed in most states.

(Reporting by Julia Harte and Jason Lange; Additional reporting by Grant Smith in New York; Editing by Damon Darlin and Ross Colvin)